The present invention relates generally to monitoring the cleaning, disinfecting, and sterilizing of instruments and equipment. More particularly, the present invention relates to methods and devices for monitoring the efficacy of which medical devices are cleaned, disinfected, or sterilized.
Known methods for disinfecting or sterilizing medical devices for re-use have historically used high pressure steam to render the surfaces of a medical device free of all forms of viable microorganisms (sterilization) or free from microorganisms except spore forming microorganisms (high level disinfection). In the last 40 years, medical devices have become more complex with respect to design and materials that are heat sensitive. Newer low temperature disinfection methods have accordingly been developed including ethylene oxide gas, vapor phase hydrogen peroxide, vapor phase peracetic acid and liquid disinfectants such as glutaraldehyde and peracetic acid solutions for reprocessing heat sensitive devices. However, many medical instruments are made of materials that may be damaged by exposure, especially repeated exposure, to high-pressure steam or gaseous disinfection procedures.
Devices that automatically clean and then disinfect medical and other equipment have been developed. Typically, these systems simply carry out a wash cycle for a preset duration. Cleaning is not always certain, especially when the water is not at the ideal temperature, the detergent is not at full strength, water pressure is abnormally low, the cleaning cycle is aborted due to an ineffective timing device, or if other error conditions are present.
One error condition is the failure to reduce the biological burden on incoming devices to an acceptable level. All health care reprocessing guidelines call for the precleaning of medical devices by a manual process that can reduce the bioburden level by 3 logs. Without a consistent manual precleaning process, any subsequent disinfection and sterilization is likely to fail. This is probably the greatest source of variability in the overall reprocessing sequence.
One particular class of medical devices, flexible endoscopes, has advanced the ability of medial practitioners for diagnosis but has also proved more difficult to adequately clean. Endoscopes are protectively encased bundles of flexible optical fibers used to transmit images to the operator at one end from otherwise inaccessible regions into which the opposite end of the instrument is inserted, so as to obtain a view of the structures surrounding such regions. Such an arrangement makes possible the visual examination, and even photographing, of structures surrounding cavities to which there is some external access, such access typically being a relatively small opening at some distance from the region of interest.
Endoscopes typically include means for allowing insertion of fluids into the region of interest and means for removal of tissue. Thus, in addition to the fiber optic bundle, there is usually provided a plurality of enclosed channels or passageways more or less paralleling the direction of the fiber optic bundle. These channels are also included within the enclosure that protects the fiber optic bundle. Specifically, such channels are typically provided to carry one or more of water, air, and carbon dioxide gas. A further channel is often provided to permit the extension therethrough of the instrumentation needed to conduct a biopsy of tissue in the region of interest. This latter channel may also be connected to a vacuum source as a means for obtaining fluid samples. This biopsy/suction source typically has a larger diameter than the other channels.
Because endoscopes are complex, highly instrumented medical devices, they are too costly to be disposable. Therefore, it is desirable to reuse such devices. Because they are exposed to bodily fluids and tissue, both internally and externally, it is necessary to clean these devices thoroughly before reuse.
Automated endoscopic reprocessors have been developed specifically to clean and disinfect flexible endoscopes to a level that mitigates the transmission of pathogenic organisms and disease between patients who are subject to an endoscopic procedure. U.S. Pat. No. 4,763,678, which is hereby incorporated by reference, discloses an exemplary endoscope reprocessor.
Automated endoscopic reprocessors (AERs) have significantly advanced the state of the art of reprocessing complex medical devices. Prior to the development of AER""s, flexible endoscopies were cleaned and disinfected in an uncontrolled manual process of cleaning, disinfecting and rinsing in disinfectant. AER""s provide an environment wherein the critical reprocessing parameters of liquid disinfectant use-life, rinse volumes, disinfectant contact time, disinfectant temperature and disinfectant volumes are controlled. The effectiveness of marketed disinfectants are carefully controlled by government regulatory agencies requiring scientific data related to the ability of the disinfectant to kill pathogenic under challenging conditions and related to the ability of AER""s to deliver legally marketed disinfectants to the flexible endoscope being reprocessed.
U.S. Pat. No. 6,068,815 describes a chemical concentration detector using infrared light to determine concentration of the active agent. Monitoring of liquid chemical disinfection or sterilization can also be carried out by measuring the physical parameters of a reprocessing device as described in U.S. Pat. No. 6,156,267. When acceptable parameter levels have been met, the processed load is assumed to be disinfected or sterilized thus claiming to eliminate the need for biological indicators and chemical indicators or integrators. A drawback of this monitoring approach is that it fails to account for the variability associated with the type, resistance or amount of biological organisms that might be present in the medical device being reprocessed.
An additional method of monitoring the effectiveness of a particular disinfectant is through the use of biological indicators. Biological indicators are typically strips of paper or other porous media containing a controlled number of bacterial spores that provide a high level of challenge to the disinfectant process. Spores of bacillus subtilis, bacillus circulans and bacillus stearotherophilus have been used to monitor high-level disinfection processes including liquid disinfection and sterilization. A specific device to determine the effectiveness of a decontamination process with a self-contained biological indicator and a spore trapping microporous membrane is described in U.S. Pat. No. 5,736,355. While this device is useful for determining spore survival in the presence of a disinfectant, it does not address the problem of monitoring biological activity or the absence of biological activity within a thin, narrow endoscope lumen.
While some AER manufacturers have developed either chemical or biological indicators, as described above, to monitor the effectiveness of a particular high-level disinfection AER process or cycle, their use is problematic. Existing chemical or biological indicators for AER""s do not take into account the challenge introduced by long, narrow lumens that provide an environment wherein microorganisms are difficult remove and can easily colonize the entire endoscope.
A relatively new problem in reprocessing of flexible endoscopes is related to advances in our understanding of a new class of materials called xe2x80x9cbiofilmsxe2x80x9d. Biofilms are microbiologically generated polysaccharide matrices that form when bacteria adhere to surfaces in aqueous environments and begin to excrete a slimy, glue like substance that can anchor them to all kinds of materials such as those found in medical devices and tissue. A biofilm can be formed by a single bacterial species, but more likely will consist of many species of bacteria, as well as fungi, algae, protozoa and inorganic products. Biofilms can form on any surface exposed to bacteria, nutrients and water under the right conditions. Many species of bacteria are becoming recognized as capable of existing in a free suspended state called the planktonic state or in a biofilm matrix referred to as the biofilm state. It is a characteristic of biofilms that the planktonic and non-planktonic states can be reversed under the right conditions. Once anchored to a surface, biofilm microorganisms can colonize and grow into a complex colony that contain and protect bacteria from outside attack.
Biofilms were first recognized as problematic in the industrial environment where fungi and algae can cause problems in cooling towers or water treatment and storage facilities. Recently, biofilms have become indicated as an infection control issue for implantable medical devices such as urinary catheters, implantable cardiac devices and cerebral shunts.
U.S. Pat. Nos. 5,928,948 and 5,923,432 describe a method for the assessment and validation of a cleaning process using a porous substrate containing contaminated soils and shielded from the environment by an impermeable layer. The cleaning process is evaluated by examining the porous material with an infrared or other electronic reader to determine the presence of remaining soil that has not been removed. The method ignores the problem of biofilm formation and only uses a challenge package in lieu of replicating the endoscope environment.
Several methods have recently been developed to form biofilms on projections by providing a flow of liquid growth medium across materials and assays made of the resulting biofilm as described in U.S. Pat. No. 6,051,423. While these methods do provide for the preparation and analysis of biofilm materials in a controlled laboratory environment they do not address the problem of biofilm removal and assay in the real world hospital environment involving reprocessable flexible endoscopes.
The present invention is directed to a cleaning efficacy indicator system and method that automatically assesses the cleaning in a real-time, cost-effective, and highly accurate manner. It is therefore an object of the invention to provide a device that monitors the ability of automated endoscopic reprocessors to remove bacterial biofilms within the long, narrow lumens of a flexible endoscope. The device is intended to provide a challenge to biofilm removal within a long, narrow environment that simulates the environment found within a flexible endoscope. It is a further object of the invention to utilize a biofilm detecting substance or dye that can be quantitatively analyzed within the challenge device without contaminating either the endoscope or the surrounding environment with either the planktonic or biofilm containing bacteria.
One aspect of the invention is to provide an apparatus that simulates the most difficult to clean lumens of a flexible endoscope. The simulated device is composed of endoscope lumen materials, approximating the length of flexible endoscope lumens but without the costly optical train of flexible endoscopes.
Another aspect of the invention is to provide an apparatus that is constructed of components that are optically transmissive and can be easily analyzed through an external optical analysis of internal biological activity.
A further aspect of the invention is to provide a device that can be connected into a flexible endoscopic reprocessor to evaluate cleaning effectiveness against biofilm challenge agents but without contamination of either the endoscope being reprocessed or the automated endoscopic reprocessor.
An additional aspect of the invention is to provide a device with a frangible chamber containing stains or dyes specific for biofilms. Said frangible chamber is contained within but separated from the simulated endoscope to release biofilm dyes when needed for analysis.
Another aspect of the invention is to provide an optical detector that is capable of quantitative detection of biofilm specific dyes or stains. Said detector is designed to fit and can be used either inside or outside of an automated endoscopic reprocessor.
One advantage of the present invention is to provide a flexible simulated endoscope that exactly simulates the physical environment and biological conditions of endoscope lumens and can be easily analyzed and cost effectively disposed of after analysis.
Another advantage of the present invention is to provide a biofilm containing simulated endoscope that can be immediately analyzed for biofilm activity after the simulated endoscope has been reprocessed either internal or external to an automated endoscope reprocessor.
A further advantage of the present invention is to provide a biofilm containing simulated endoscope that can be reprocessed without the risk of cross contamination of flexible endoscopes or the reprocessors with biofilm test substrates.
An additional advantage of the present invention is to deliver a biofilm indicating dye when needed to analyze for biofilm residuals after reprocessing.